Short Attention Span Summary

Stuck to the magnetThe FDA has recently approved some MRI-safe pacemakers, but what if a patient needs MRI and doesn't have one of these? This was a series of 1000 patients with pacemakers, 500 of which also had an ICD, undergoing non-thoracic MRI at 1.5 Tesla. The devices were interrogated and programmed according to a protocol prior to MRI. There were no cases of death, device, or lead failure. There were 6 cases of afib/flutter that all resolved spontaneously, and 6 cases of partial electrical reset of the device. One device, which was not programmed prior to MRI, could not be interrogated after the scan and had to be immediately replaced.

Spoon FeedA patient with a pacemaker/ICD that is not specifically approved as MRI-safe should still not routinely undergo MRI. But this study shows that a non-thoracic MRI is not absolutely contraindicated, assuming proper interrogation and programming of the device is done before the scan. This is not something we can order without buy-in and help from cardiology. See the Journal Watch summary.

The presence of a cardiovascular implantable electronic device has long been a contraindication for the performance of magnetic resonance imaging (MRI). We established a prospective registry to determine the risks associated with MRI at a magnetic field strength of 1.5 tesla for patients who had a pacemaker or implantable cardioverter-defibrillator (ICD) that was "non-MRI-conditional" (i.e., not approved by the Food and Drug Administration for MRI scanning).

Methods

Patients in the registry were referred for clinically indicated nonthoracic MRI at a field strength of 1.5 tesla. Devices were interrogated before and after MRI with the use of a standardized protocol and were appropriately reprogrammed before the scanning. The primary end points were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary end points were changes in device settings.

Results

MRI was performed in 1000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. We observed six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events.

Conclusions

In this study, device or lead failure did not occur in any patient with a non-MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5 tesla, was appropriately screened, and had the device reprogrammed in accordance with the prespecified protocol. (Funded by St. Jude Medical and others; MagnaSafe ClinicalTrials.gov number, NCT00907361 .).